This invention relates to a process and a laminator for the continuous production of laminates of foam with facings. An upper facing and a lower facing and a web of meshwork are introduced into the foaming space of a laminator and a fluid reaction mixture is spread over the lower facing before it runs into the foaming space. The reaction mixture penetrates the web of meshwork as it foams up on its journey through the foaming space and becomes bonded to the facings. The process may be used to produce polyurethane foams, polyisocyanurate foams, phenol resin foams or the like, depending on the starting components used for the fluid reaction mixture from which the foam is formed.
It is well known to cover the back of facings with non-woven fiber webs or to run them into the foaming space together with reinforcing webs such as glass fiber fabric. This procedure is intended to increase the mechanical strength especially immediately underneath the facings and to improve the bond between the facings and the foam core as well as to obtain a profile of decreasing density from the facing layers to the center of the foam. The use of non-woven fiber webs serves mainly for reinforcement. Such webs therefore have a finer mesh and a larger weight per square meter and are made of a high quality material, preferably glass fibers. The generic term, "meshwork web" covers webs of woven fabric, knitted fabric, grids and woven and non-woven fiber fleeces in the widest sense.
It has been found that when facings are used which are impermeable or almost impermeable to gas, gas bubbles of considerable size accumulate underneath the upper facing as the foam expands. These gas bubbles subsequently make their mark on the visible surface of the product if the facings are thin sheets. The irregular bulges formed on the surface not only mar the appearance of the product but since they are formed by cavities they increase the risk of damage to the facings at these points. It has been found that even the use of the conventional meshwork webs such as glass fiber fabrics and non-woven fiber fleeces cannot prevent the formation of gas bubbles. It was found that, depending on the particular nature of these webs, they sometimes showed patches that were completely free from foam, evidently because they had been completely penetrated by gas bubbles. In other cases, the reaction mixture had rrept along inside a web, evidently due to capillary action, and formed a film of foam underneath which the gas bubbles accumulated. Although in the latter case the film of foam together with the reinforcing web had to some extend stabilized the facing, these hollow patches were still more liable to be damaged by sudden, forceful impacts. When the laminating process described above was carried out, the formation of bubbles was found only underneath the upper facing. Gases developing in the course of the reaction of the chemical system and air bubbles enclosed in the application of the reaction mixture evidently have enough time to rise within the expanding reaction mixture and reach the surface or come close to the surface before the reaction mixture hardens.
The problem therefore arises of improving the above-described process and laminator so that laminates of foam with facings will be free from bubbles underneath the upper facing.